Typical home entertainment systems include a television, a VHS tape machine, and some type of set-top box (e.g., a cable box). Sophisticated systems might also include such components as a radio receiver, a CD player, a pair of speakers, a karaoke, and a DVD player. The possibility of adding and combining many disparate audio and video input sources requires that at least one of the interconnected components enable users to select from various input sources and to appropriately configure the desired audio/video output source. Unfortunately, finding the correct configuration of components to display a desired audio/video presentation often requires a viewer to employ a number of different remote-control devices and user interfaces to arrive at the correct combination of device configurations. Experienced users of such systems can attest to the difficulty of finding the appropriate settings for each case; less experienced users find the task even more exasperating.
In view of the above, there is a need to provide consumers with simplified systems of devices, and preferably systems that can be controlled using a single, simple user interface. The IEEE 1394 system architecture, also known as the “FireWire® System Architecture,” addresses this need. (“FireWire” is a registered trademark of Apple Computer.) FireWire®-compliant devices assign six-bit physical identifiers to each device connected to a FireWire® serial bus. The FireWire®-compliant devices then use these physical identifiers to uniquely identify themselves on the bus. Whenever a new device is added to the bus, an existing device is removed from the bus, or both, a bus reset initiates certain well-known bus recovery communications and functions in accordance with the FireWire® standard. The bus reset then repeats the process of uniquely identifying each device on the bus.
The ability to uniquely identify each device in a home entertainment system greatly reduces the complexity required to display a desired program. For example, if a viewer issues a command to a FireWire®-capable television (via an infrared remote control, for example) to play a video disk in a FireWire®-capable DVD player, then the television would automatically communicate with the appropriate player over the bus to receive and display the contents of the video disk.
Most consumers who might consider purchasing an advanced entertainment system already own one or more older “legacy” devices and may have content stored using a legacy format. For example, a consumer interested in purchasing a recent model digital television may have a VHS machine, a collection of analog VHS tape recordings, and a set-top box equipped to deliver analog broadcast programming. The consumer will not likely wish to part with some or all of these. It is therefore important for manufacturers of the latest consumer electronics to provide support for older “legacy” devices.
FIG. 1 (prior art) depicts a system 100 in which a digital television (DTV) 105 and digital VCR (DVCR) 110 communicate via a digital FireWire® channel 115 and, to support legacy VHS recordings, an analog channel 120. Both digital television 105 and digital VCR 110 are assumed to communicate using the IEEE 1394a standard. In one example, the devices of system 100 communicate in accordance with EIA 775, which defines a specification for a baseband digital interface to a digital television using the IEEE 1394 standard.
DTV 105 includes a display 125, a digital interface 130, and a switch 135. Interface 130 controls switch 135 to select between digital channel 115 and analog channel 120. DVCR 110 conventionally includes a panel subunit 140 and a VCR subunit 145. Panel subunit 140 communicates with digital interface 130 using the FireWire® standard, and VCR subunit 145 reads both analog and digital video recordings. VCR subunit 145 provides digital signals to DTV 105 via panel subunit 140 and digital channel 115, and provides analog signal to DTV 105 via analog channel 120.
In the absence of some sort of intelligent interface, the user of system 100 would have to know at any given moment whether the output of the DVCR 110 was an analog signal or a digital signal. The user would then have to instruct DTV 105 to select the appropriate analog or digital input. Requiring the user to make such decisions can be confusing, especially if DVCR 110 can play tapes that include both analog and digital information.
The FireWire® standard addresses this problem by providing an intelligent means of automatically switching between analog channel 120 and digital channel 115 without requiring user input. When switching between analog and digital outputs, DVCR 110 can issue a FireWire® standard “CONNECT” command over digital channel 115 to instruct digital interface 130 to issue the appropriate video-select command on port VS to switch 135. The user is thus relieved from the burden of having to manually switch between video signals. FireWire®-compliant systems that employ the EIA 775 protocol issue a CONNECT command with an EIA 775 “descriptor” specifying the analog_input_plug_ID as the destination plug.
FIG. 2 depicts an entertainment system 200 in which a digital television 205 is connected to two audio/video devices 210 and 215. In the depicted example, DTV 205 is a FireWire®-compliant digital television, and devices 210 and 215 are a FireWire®-compliant digital VCR and a FireWire®-compliant digital set-top box, respectively. All three devices include analog communication channels to support legacy communication.
DTV 205 includes an analog tuner 220, some FireWire®-compliant digital interface circuitry 225, a video selection circuit 230 controlled by a user interface 235, a video processor 242 to interpret incoming video signals, and a display 244 for presenting the interpreted video signals to users (i.e., viewers). Video selection circuit 230 includes three analog video channels AV0-AV2 connected to three respective analog input jacks 245. Video selection circuit 230 also includes a digital video channel DV# that receives digital video signals from three digital communication jacks 250 via digital interface circuitry 225 and a FireWire® bus 255.
User interface 235 receives commands from the control panel (not shown) on DTV 205 and via an infrared receiver 260 that receives infrared instructions from a remote control 265. User interface 235 connects to video selection circuit 230 and issues video select commands VS as directed by the user. In some embodiments, selection circuit 230 enables DTV 205 to simultaneously display the contents of more than one video input to selection circuit 230. For example, DTV 205 can simultaneously display a user interface and broadcast video from an analog or digital broadcast, and embodiments that support picture-in-picture (PIP) can simultaneously receive and display data from two analog channels, two digital channels, or one analog and one video channel.
Digital interface circuitry 225 communicates with devices 210 and 215 via digital video channels DV1 and DV2. Because interface circuitry 225 and devices 210 and 215 are all FireWire® compliant, interface circuitry 225 can distinguish between devices 210 and 215. User instructions received by user interface 235 can therefore be directed to the appropriate one of devices 210 and 215, and digital interface circuitry 225 can direct digital video streams from devices 210 and 215 to video selection circuit 230. Assuming, for example, that device 210 is a digital video recorder, a user can instruct DTV 205 to play videotape in device 210. Such an instruction would cause user interface 235 to command video selection circuit 230 to select digital video input DV# and to issue a “play” instruction to device 210 via digital interface circuitry 225 and bus 255. In this way, the user can specify the output of either device 210 or 215 with a simple command to DTV 205.
A problem can arise when one of devices 210 or 215 provides an analog output signal on its respective analog video output AV. As noted above, the FireWire® standard allows compliant devices to issue a “CONNECT” command causing DTV 205 to switch to an analog input. However, DTV 205 has no way of telling which of analog input jacks 245 is connected to the requesting device. Thus, a request to switch the input of DTV 205 to one of analog input jacks 245 may cause DTV 205 to display the correct video, video from the wrong device, or nothing at all. For example, if device 210 issues a command to switch to an analog input while device 215 is also active, DTV 205 might display broadcast video from antenna 270 or the analog signal from device 215. The user would then have to either physically swap analog input connectors to jacks 245 until the appropriate signal is displayed, or would have to employ user interface 235 to manipulate video selection circuit 230. The user would then have to repeat this process from time to time, depending on the selected device and the analog input currently selected by circuit 230.
Requiring the user to manually select the appropriate video input or rearrange physical connections can be confusing; indeed, this is part of the reason the FireWire® standard was adopted. Unfortunately, the unique identifiers used by FireWire®-compliant devices do not exist for analog signals. There is therefore a need for a way to uniquely identify a number of analog channels to relieve the user of the burden of manually selecting from among them.